Processes for the alkylation of aromatic feedstocks and the use of molecular sieves as catalysts in such alkylation processes are well known in the art. Such alkylation processes may be used to produce mono- or polyalkylated products ranging from low to high molecular weights and may be carried out in the vapor phase, in the liquid phase, or under intermediate conditions in which both liquid and vapor phases exist.
U.S. Pat. No. 4,301,316 to Young discloses the use of a crystalline zeolite alkylation catalyst in the alkylation of benzene by relatively long chain length alkylating agents having one or more reactive alkyl groups of at least five carbon atoms. The reactants may be in either the vapor phase or the liquid phase, and the zeolite catalyst may be either modified or unmodified. Preferred zeolite catalyst include zeolite beta, ZSM-4, ZSM-20, ZSM-38, and synthetic and naturally occurring isotopes thereof, such as zeolite omega and others. The zeolites may be subjected to various chemical treatments, and may also be subjected to thermal treatment, including steam or calcination in air, hydrogen and an inert gas. Specifically disclosed in Young is the reaction of benzene and 1-dodecene over zeolite beta in a flow reactor at 250.degree. C. and 600 psig.
U.S. Pat. No. 4,185,040 to Ward et. al. discloses an alkylation process employing a molecular sieve catalyst of low sodium content which is said to be especially useful in the production of ethylbenzene from benzene and ethylene, and cumene from benzene and propylene. The Na.sub.2 O content of the zeolite should be less than 0.7 weight percent and preferably less than 0.5 weight percent. Examples of suitable zeolites include molecular sieves of the X, Y, L, B, ZSM-5, and Omega crystal types, with steam stabilized hydrogen Y zeolite being preferred. The alkylation process is preferably carried out under conditions in which at least some liquid phase is present, at least until substantially all of the olefin alkylating agent is consumed.
Another alkylation procedure is disclosed in U.S. Pat. Nos. 4,798,816 and 4,876,408 to Ratcliffe et. al. Ratcliffe et. al. employ molecular sieve alkylation catalyst which have been treated in a manner to improve selectivity to monoalkylation, specifically to the propylation of benzene to produce cumene. Selectivity is said to be increased by at least one percentage point by first depositing a carbonaceous material on the catalyst and then subjecting the resultant carbon containing catalyst particles to combustion. Specifically disclosed zeolitic crystalline molecular sieves include those selected from the group of Y zeolites, fluorided Y zeolites, X zeolites, zeolite beta, zeolite L and zeolite omega. The zeolites may be modified to arrive at products of reduced alumina content and reduced sodium content.
Aromatic alkylation reactions such as the alkylation of benzene with ethylene are highly exothermic reactions. As a result the alkylation reactions may be carried out in stages with intermediate cooling steps. For example, U.S. Pat. No. 4,107,224 to Dwyer discloses the vapor phase ethylation of benzene over a zeolite catalyst in a down flow reactor with the intermediate injection of cold reactants in a diluent. Specifically disclosed is the interstage injection of ethylene and benzene. Dwyer characterizes the catalyst suitable for use in his invention in terms of those having a constraint index within the approximate range of one to twelve. Suitable zeolites, with the constraint index in parenthesis, are ZSM-5 (8.3), ZSM-11 (8.7), ZSM-12 (2), ZSM-35 (4.5), ZSM-38 (2) and similar materials. Various molecular sieves including, inter alia, zeolite beta (constraint index 0.6), are disclosed as having constraint indices outside of the range suitable for the Dwyer ethylbenzene production process.
U.S Pat. No. 4,891,458 to Innes is directed to a process for the alkylation or transalkylation of an aromatic hydrocarbon with a C.sub.2 to C.sub.4 olefin alkylating agent under at least partial liquid phase conditions utilizing zeolite beta as the catalyst.